Re: 3-D phenomenon

[P3D Gregory J. Wageman <gjw@xxxxxxxxxx>]

Allan Woods writes:

>True, but if you took a "Realist' picture of that distant scene, there
>would be no discernible depth in the distance - that is why optimum
>subject distance is approx. 7 ft. and put something in the foreground.

Then later, elaborates:

>I was in the desert not long ago looking at HUGE piles of HUGE boulders
>some half-mile away.  I could not tell where the canyons and ridges were
>between the bolder foothills.  Look through binoculars or walk there
>and in fact there were a series of ridges.

So I have to wonder, what is the Realist format discarding?  By your own
descriptions here, it seems to have the same limitation as our vision
system.

>YOU can tell depth in the distance because of another 'depth' clue -
>that things father away are less chromatically intense.  You also know
>mountains are far away.

A slide captures all these clues also.  I remember when I first
drove up to Shasta Dam in northern California.  From the scenic overlook,
one could look out over the dam to Shasta Lake, and in the distance
Mount Shasta could be seen.  My wife and I both commented that Mt. Shasta
in the distance looked *exactly* like a matte painting!  Life imitates
art, I guess. :-)

Seriously, though, it's because matte artists are utilizing the exact
clues you mention: a softening of focus to simulate atmospheric
diffraction, and a lessened chromatic intensity due to absorption.

>What I was saying is that there are many ways to get the 'depth' information
>and 'out of focus' should not be discarded as just 'noise.'  If you
>provide a means for your brain to interpret the focus information, it
>is possible to percieve that 'depth' thing which is the 'illusion' of
>3-D.

But the reason we 'discard' it in a Realist slide is because our vision is
dynamic!

When I sit here and focus on my finger and blur the background, "reality"
doesn't go out-of-focus (imagine if it did, and anybody could blur out
reality on you at any time!).  All of reality is "in-focus" all of the
time; it is our *vision system* that is selectively focusing, and yes,
that does give us a depth cue.  But we do exactly the same thing when we
view a Realist slide *if* it contains both near (in front of the window)
and far subjects (behind the window).  I recently took such a shot, as
an experiment.  I framed a tree through the hole in a concrete playground
sculpture/climbing thing that looks roughly like a 4 foot tall slice of
brown Swiss cheese.  Both the sculpture (which is in front of the window)
and the tree (about 100ft away) are in sharp focus.  But when you shift
your viewpoint to the sculpture, the tree goes blurry and double, and
vice-versa.  It's rough on the eyes, but it demonstrates to me that the
Realist format isn't 'discarding' anything.

The entire slide must be in focus (like reality) if we are ever to see
the detail in the distance.  In fact, having thought this through I would
now state that the opposite is true: by using selective focus in a Realist
slide, you would be forcing the viewer to look only at the in-focus subject,
and then you are, in fact, 'discarding' the detail in the distance.

	-Greg


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